1,230 research outputs found
Spacecraft drag-free technology development: On-board estimation and control synthesis
Estimation and control methods for a Drag-Free spacecraft are discussed. The functional and analytical synthesis of on-board estimators and controllers for an integrated attitude and translation control system is represented. The framework for detail definition and design of the baseline drag-free system is created. The techniques for solution of self-gravity and electrostatic charging problems are applicable generally, as is the control system development
Oxford Handbook Of American Political Development
Scholars working in or sympathetic to American political development (APD) share a commitment to accurately understanding the history of American politics – and thus they question stylized facts about America’s political evolution. Like other approaches to American politics, APD prizes analytical rigor, data collection, the development and testing of theory, and the generation of provocative hypotheses. Much APD scholarship indeed overlaps with the American politics subfield and its many well developed literatures on specific institutions or processes (for example Congress, judicial politics, or party competition), specific policy domains (welfare policy, immigration), the foundations of (in)equality in American politics (the distribution of wealth and income, race, ethnicity, gender, class, and sexual and gender orientation), public law, and governance and representation. What distinguishes APD is careful, systematic thought about the ways that political processes, civic ideals, the political construction of social divisions, patterns of identity formation, the making and implementation of public policies, contestation over (and via) the Constitution, and other formal and informal institutions and processes evolve over time – and whether (and how) they alter, compromise, or sustain the American liberal democratic regime. APD scholars identify, in short, the histories that constitute American politics. They ask: what familiar or unfamiliar elements of the American past illuminate the present? Are contemporary phenomena that appear new or surprising prefigured in ways that an APD approach can bring to the fore? If a contemporary phenomenon is unprecedented then how might an accurate understanding of the evolution of American politics unlock its significance
Autonomous frequency domain identification: Theory and experiment
The analysis, design, and on-orbit tuning of robust controllers require more information about the plant than simply a nominal estimate of the plant transfer function. Information is also required concerning the uncertainty in the nominal estimate, or more generally, the identification of a model set within which the true plant is known to lie. The identification methodology that was developed and experimentally demonstrated makes use of a simple but useful characterization of the model uncertainty based on the output error. This is a characterization of the additive uncertainty in the plant model, which has found considerable use in many robust control analysis and synthesis techniques. The identification process is initiated by a stochastic input u which is applied to the plant p giving rise to the output. Spectral estimation (h = P sub uy/P sub uu) is used as an estimate of p and the model order is estimated using the produce moment matrix (PMM) method. A parametric model unit direction vector p is then determined by curve fitting the spectral estimate to a rational transfer function. The additive uncertainty delta sub m = p - unit direction vector p is then estimated by the cross spectral estimate delta = P sub ue/P sub uu where e = y - unit direction vectory y is the output error, and unit direction vector y = unit direction vector pu is the computed output of the parametric model subjected to the actual input u. The experimental results demonstrate the curve fitting algorithm produces the reduced-order plant model which minimizes the additive uncertainty. The nominal transfer function estimate unit direction vector p and the estimate delta of the additive uncertainty delta sub m are subsequently available to be used for optimization of robust controller performance and stability
Charges of twisted branes: the exceptional cases
The charges of the twisted D-branes for the two exceptional cases (SO(8) with
the triality automorphism and E_6 with charge conjugation) are determined. To
this end the corresponding NIM-reps are expressed in terms of the fusion rules
of the invariant subalgebras. As expected the charge groups are found to agree
with those characterising the untwisted branes.Comment: 15 page
ArCLight - a Compact Dielectric Large-Area Photon Detector
ArCLight is a novel device for detecting scintillation light over large areas
with Photon Detection Efficiency (PDE) of the order of a few percent. Its
robust technological design allows for efficient use in large-volume particle
detectors, such as Liquid Argon Time Projection Chambers (LArTPCs) or liquid
scintillator detectors. Due to its dielectric structure it can be placed inside
volumes with high electric field. It could potentially replace vacuum
PhotoMultiplier Tubes (PMTs) in applications where high PDE is not required.
The photon detection efficiency for a 10x10cm2 detector prototype was measured
to be in the range of 0.8% to 2.2% across the active area
2,3-butanediol in experimental myocardial ischaemia in pigs
To investigate the role of 2,3-butanediol in myocardial ischaemia we analysed this compound in pig's myocardium and blood. Ischaemia was induced by ligation of a coronary artery. In the first study we found significantly higher levels of 2,3-butanediol in the homogenate of ischaemic myocardium than in non-ischaemic myocardium. The lactate concentration was also significantly elevated. In the second study, where ischaemia was similarly induced, and where reperfusion was achieved by re-opening the ligated coronary artery after 20 min, 2,3-butanediol in peripheral blood was found to increase significantly. In the pigs in which the coronary artery was not re-opened, the 2,3-butanediol level in peripheral blood was unchanged. We conclude that in pigs' anaerobic myocardia accumulation of 2,3-butanediol occurs; if the myocardium is reperfused this metabolite also appears in the bloo
First Operation of a Resistive Shell Liquid Argon Time Projection Chamber -- A new Approach to Electric-Field Shaping
We present a new technology for the shaping of the electric field in Time
Projection Chambers (TPCs) using a carbon-loaded polyimide foil. This
technology allows for the minimisation of passive material near the active
volume of the TPC and thus is capable to reduce background events originating
from radioactive decays or scattering on the material itself. Furthermore, the
high and continuous electric resistivity of the foil limits the power
dissipation per unit area and minimizes the risks of damages in the case of an
electric field breakdown. Replacing the conventional field cage with a
resistive plastic film structure called 'shell' decreases the number of
components within the TPC and therefore reduces the potential points of failure
when operating the detector. A prototype liquid argon (LAr) TPC with such a
resistive shell and with a cathode made of the same material was successfully
tested for long term operation with electric field values up to about 1.5
kV/cm. The experiment shows that it is feasible to successfully produce and
shape the electric field in liquefied noble-gas detectors with this new
technology.Comment: 13 page
lmmuno Histochemical Profile of Endometrium in Patients With Genital Endometriosis
The aim of present study was to investigate the occurence of different lymphocyte
subsets in the endometrium of endometriosis patients and in healthy women on every
day of the menstrual cycle with special emphasis to the proliferative activity of
endometrial cells with Ki-S3 antibody. We also conducted immunohistochemical
studies of T-lymphocytes, B-lympho-cytes, macrophages, natural-killer-cells and also
of antigens class II of the histocompatibility complex (HLA-DR) during the different
phases of the menstrual cycle in endometriosis and non-endometriosis patients
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Modelling and Analysis of Vibrations in a UAV Helicopter with a Vision System
The analysis of the nature and damping of unwanted vibrations on Unmanned Aerial Vehicle (UAV) helicopters are important tasks when images from on‐board vision systems are to be obtained. In this article, the authors model a UAV system, generate a range of vibrations originating in the main rotor and design a control methodology in order to damp these vibrations. The UAV is modelled using VehicleSim, the vibrations that appear on the fuselage are analysed to study their effects on the on‐board vision system by using Simmechanics software. Following this, the authors present a control method based on an Adaptive Neuro‐Fuzzy Inference System (ANFIS) to achieve satisfactory damping results over the vision system on board
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